OP0212 EXAMINING CLINICAL HETEROGENEITY IN PRIMARY SJOGREN’S SYNDROME: PROTEOMIC AND NETWORK ANALYSIS
Authors: J. Berry, J. Casement, E. Traianos, J. Tarn, W. F. Ng
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> A symptom-based stratification tool using data from three European cohorts identified four clinical subtypes of pSS: Low symptom burden (LSB), high symptom burden (HSB), dryness dominant with fatigue (DDF), and pain dominant with fatigue (PDF).[1] These subtypes have distinct molecular profiles, clinical manifestations, and responses to immunomodulatory therapies. Detailed knowledge of the biological pathways underlying the clinical subtypes is vital to understanding the clinical heterogeneity of pSS and has relevance for trial design and therapeutic development. <h3>Objectives</h3> Clinical manifestations of an immune-mediated inflammatory disease are likely underpinned by networks of dysregulated biological pathways. Proteomic and network analysis was performed to identify biological pathways that are differentially expressed between the pSS subtypes. <h3>Methods</h3> We profiled serum proteins using O-link technology of 180 pSS subjects (45 subjects of each subtype). We used 5 O-link proteomics panels which included 454 proteins. As we anticipate that these serum proteins may act directly or indirectly through interactions with other proteins, we used a network analysis approach. Using the LSB group as a reference we identified differentially expressed proteins. Network reconstruction was performed using the ARACNE algorithm which calculates mutual information between the variables of a multidimensional dataset to construct a protein network.[2] Differential expression estimates were overlaid on these networks to reveal key regions that are differentially expressed between the phenotypes. Statistical analysis was performed in R v4.1.3 and JMP Pro v15 and network visualisation in cytoscape v3.8.2. <h3>Results</h3> The DDF group is characterised clinically by glandular dysfunction. The DDF proteome demonstrated higher expression of chemokines that orchestrate lymphocyte migration and ectopic lymphoid structure formation in the salivary glands and of cytokines promoting B-cell hyperactivity and autoantibody production. In contrast to DDF, the HSB and PDF groups report extra-glandular manifestations such as pain, fatigue, and mood disturbances. HSB and PDF proteomes show increased expression of proteins linked to the inflammatory response, oxidative stress response and cellular metabolism (IL-1α, IL-6, APE/Ref-1, FOXO1, TIGAR and BACH1). Network analysis revealed distinct clusters of proteins that were upregulated or downregulated between different pSS subtypes, providing added support to the concept that distinct molecular pathways contribute to the clinical manifestations of these subtypes. <h3>Conclusion</h3> Protein expression between the clinically distinct pSS subgroups revealed differences in cytokines, chemokines and master transcription factors associated with redox imbalance and altered energy metabolism. Furthermore, the differentially expressed proteins seem to be interrelated in our network analysis. Our data provide clues to the molecular pathways contributing to the glandular and systemic manifestations of pSS and to potential therapeutic targets for different pSS subgroups. <h3>References</h3> [1]Tarn JR <i>et al</i>. Symptom-based stratification of patients with primary Sjogren's syndrome: multi-dimensional characterisation of international observational cohorts and reanalyses of randomised clinical trials. Lancet Rheumatol. 2019 Oct 1;1(2):e85–94. [2]Margolin AA <i>et al</i>. ARACNE: An algorithm for the reconstruction of gene regulatory networks in a mammalian cellular context. BMC Bioinformatics. 2006 Mar 20;7(Sp1). <h3>Acknowledgements</h3> on behalf of the UKPSSR. Work was funded by FOREUM, EU and the MRC. <h3>Disclosure of Interests</h3> None Declared.